The Dangers of CT Scans and X-rays
A CT scan can lead to a diagnosis of your symptoms, but can it also do more harm than good? Learn about common medical imaging tests and your risks of radiation exposure.
Sanaz Majd, MD
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The Dangers of CT Scans and X-rays
Say you visit your doctor for this abdominal discomfort you’ve been having for the last few days. You are ecstatic when she suggests a CT scan of your stomach as a possible test to find out what’s wrong. “Great,” you say, “now we can look into my stomach and actually see what it could possibly be!”
But have you ever considered about the price you’d have to pay for that image? I’m not talking about money. I’m talking about radiation exposure. Most patients have no idea the amount of radiation one CT scan exposes them to. Why would it matter anyways? Let’s find out in today’s episode.
What is Radiation?
Radiation is really just energy, in the form of particles or waves, moving through space. Heat and light are considered radiation, but those types of radiation are not potentially harmful to us. However, ionizing radiation is another story – this type of radiation is considered “unstable” because it has excess energy that it needs to “shake off.” And that shaking off is really what is potentially harmful to us. This is what is used in common radiologic testing – such as x-rays and CT scans. This is what we are talking about when we say something is “radioactive.” You can check out Ask Science’s excellent episode called What Is Radiation? for more.
Should We Worry About Radiation from Medical Imaging?
In the U.S., radiation exposure from medical imaging has been steadily rising for the last 30 years. In fact, half of the radiation exposure we get comes from medical imaging. Why does radiation matter? Well, it’s associated with the development of cancer. How does it do this? Radiation can cause damage to our DNA, our genetic makeup, and that can cause our cells to go out of whack and potentially become cancerous. And cancer can develop decades after the exposure, not necessarily right away. Some of the most common radiation-induced cancers are leukemias, bone cancers, thyroid cancers, breast cancers, lung cancers, and skin cancers.
Are There Any Good Studies on This Topic?
I should add that there is no good research that shows a direct cause-and-effect relationship between cancer and radiation exposure from tests, partly because it’s not very ethical to perform research on patients by giving them radiation to simply “see what happens.” Also, patients would have to be followed over many decades to see if something were to develop – that would take a lot of time. But most medical communities agree that there is a real risk. That’s why radiation exposure through imaging tests is a potentially big issue.
“Doctor, all I want is a full body scan to tell me if I have ‘anything bad’ going on?”
Did you know that one abdominal CT scan that takes just a few minutes is equal to receiving about 500 x-rays? And that’s just the abdomen. CT scans carry the greatest risk from ionizing radiation exposure. If your doctor suggests getting a CT scan, make sure you find out:
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What they are looking for exactly? Is it a pocket of pus/abscess, appendicitis, a tumor, etc.
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How likely is it that a CT will actually show what they are looking for? Sometimes CTs aren’t the best at showing some anatomical structures, such as gall bladder stones.
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How important is it to find what they are looking for? If you’ve had diverticulitis before, and your symptoms are exactly the same and mild this time around, is it necessary to do another CT scan?
Always be sure to discuss these questions with your doctor in advance.
You may be wondering about ultrasounds and MRIs? They actually don’t use ionizing radiation. MRIs use magnetic and radio waves, and ultrasounds use sound waves. And routine mammograms? Like I mentioned, a single x-ray, even if you get yearly ones starting at age 40, doesn’t amount to 500 by the time you reach 100 years old. So the radiation risk from x-rays is low, although not zero, of course. But medical societies recommend mammogram screening since they have shown to decrease risk of death from breast cancer when caught early. It’s all about weighing the risks and benefits. The risk of breast cancer development is higher than the potential harm that routine mammograms can present for most patients.
Amount of Radiation per Diagnostic Test
Here are some common tests, and how many chest x-ray equivalents they may represent:
| Country | ||
|---|---|---|
|
Diagnostic Test
|
Effective Dose of Radiation
(in Millisieverts)
|
Chest X-ray Equivalents
|
|
Chest X-ray
|
0.02
|
|
|
Low Back X-ray
|
1.8
|
90
|
|
Arm or Leg X-ray
|
0.06
|
|
|
Screening Mammogram
|
0.13
|
|
|
Head CT
|
2
|
100
|
|
Abdominal CT
|
10
|
500
|
|
Chest CT
|
20-40
|
1,000 – 2,000
|
See also: What Is Radiation?
What to Consider Before an Imaging Test
To find out whether or not a patient really needs that CT scan, it’s important that the doctor knows:
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The patient history
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Their age
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Their response to previous therapy
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The list of potential diagnoses (the “differential diagnoses”)
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The physical exam
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How good of a candidate they are for surgery?
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Is it the correct test to order in the first place?
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Will it affect their management?
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Does the patient want to act on the worst case scenario?
Also, if you’ve had prior imaging studies to view a certain organ, make sure you remind your doctor of that. It’s also worthwhile to get copies of your prior imaging studies for your doctor and your chart, so you don’t need to repeat it again.
Overall, never hesitate to have a test performed if the benefits outweigh the risks of radiation. That will require a good conversation with your doctor. So if you aren’t sure whether your doctor has truly considered all these points before ordering that imaging study, make sure to ask.
See also: 6 Tips to Get Your Doctor to Listen to You
Here’s a website by the American Society of Radiologic Technologists that patients can use to keep a log of their imaging studies in order to estimate your personal risk.
What are your thoughts on ionizing radiation exposure? Have you ever had an imaging study you wished you hadn’t? Share it with us on the House Call Doctor’s Facebook and Twitter pages!
Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.
CT Scanner image from Shutterstock
